Luminescence characterizations of freestanding bulk single crystalline aluminum nitride towards optoelectronic application

Zhang

Crystal Research and Technology

et al. 2020

AlN is a kind of promising semiconductor material for high‐efficiency optoelectronic devices and high‐power high‐frequency electronic devices. In this work, high‐quality c‐plane AlN single crystal with low‐stress is grown on tungsten (W) substrate using a spontaneous nucleation physical vapor transport (PVT) method. Temperature field simulation and theoretical analysis provide a theoretical guide for the AlN crystals growth experiment. The hexagonal appearance c‐plane AlN crystal is obtained with a size up to 3 mm × 3 mm. A large radial temperature gradient and suitable supersaturation lead to a low nucleation density and the growth of AlN crystal with large size, which can be used to regulate nucleation density and size of AlN crystals on W substrate. X‐ray diffraction (XRD), Raman and electron backscatter diffraction (EBSD) results confirm that the crystal is grown along the c‐axis direction with hexagonal wurtzite structure and high crystalline quality. The Raman micro‐mapping results indicate that the grown AlN crystal has small tensile stress, close to free‐stress, and the biaxial stress decreases from interface to surface along with the increasing of crystal thickness. This work will greatly contribute to the research of AlN crystal growth on W substrate.

Section: Resultssupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

Growth and Stress Analysis of Spontaneous Nucleation c‐Plane Bulk AlN Crystals by a PVT Method

Zhang

Crystal Research and Technology

et al. 2020

“…On the contrary, exorbitant supersaturation leads to defective densities and high-density nucleation points that fabricate polycrystalline AlN. Many experiments with different T and ΔT were carried out to investigate the adequate supersaturation range [7,8,11]. It has been proven that detached freestanding high-quality AlN single crystals with large size can be obtained when the values of supersaturation are between 0.25 and 0.3 [8].…”

Section: Resultsmentioning

confidence: 99%

“…These results show that a reverse temperature field method can control AlN nucleation and is a promising PVT growth method for large-size single crystal of AlN on polycrystaline tungsten substrates. Now, a AlN single crystal with a diameter up to 2.2 ceti-meters has been fabricated with optimizing experimental parameters [7].…”

Section: Resultsmentioning

confidence: 99%

Nucleation Control in Physical Vapor Transport Growth of AlN Single Crystals on Polycrystal Tungsten Substrates

Wu¹,

Qin²,

Tian³

et al. 2019

Self Cite

The improved resistively-heated furnace with two heaters established a vertical thermal gradient to control nucleation during AlN single crystals Physical Vapor Transport (PVT) growth on polycrystal tungsten substrates. During the high temperature (> 1850 °C) heating process, the reverse temperature field (i.e., the temperature difference between the sublimation zone and the crystalline zone ΔT < 0) was obtained to reduce the number of nuclei on the tungsten substrate. During growth, the proper positive values of ΔT T were chosen to content the supersaturation values (0.25 < S < 0.3). The reverse temperature condition during high temperature (> 1850 °C) cooling was fulfilled to avoid recrystallization on grown AlN crystal. AlN single crystals made through the method were characterized by X-ray diffractions (XRD) and Raman spectroscopy.

“…Specifically, the quality improvement of the AlN single crystal is beneficial to the development and performance enhancement of deep-ultraviolet and even vacuum-ultraviolet photodetectors [ 7 , 8 ]. Owing to the advantage of excellent electrical properties, high temperature and pressure resistance, extremely high piezoelectric effect, and high electron mobility, AlN is attractive for the application of high-temperature, high-frequency and high-power devices [ 9 , 10 ]. Moreover, the lattice constant and thermal expansion coefficient of AlN are close to other Ⅲ–Ⅴ materials, thereby making it suitable as a substrate for the epitaxial growth of materials, such as GaN and AlGaN [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Simulation and Experiment for Growth of High-Quality and Large-Size AlN Seed Crystals by Spontaneous Nucleation

Qin

Chen

Deng

et al. 2020

Sensors

Self Cite

Seed crystals are the prerequisite for the growth of high quality and large size aluminum nitride (AlN) single crystal boules. The physical vapor transport (PVT) method is adopted to grow AlN seed crystal. However, this method is not available in nature. Herein, the temperature field distribution in the PVT furnace was simulated using the numerical analysis method to obtain free-standing and large-size seeds. The theoretical studies indicate that the temperature distribution in the crucible is related to the crucible height. According to the theory of growth dynamics and growth surface dynamics, the optimal thermal distribution was achieved through the design of a specific crucible structure, which is determined by the ratio of top-heater power to main-heater power. Moreover, in our experiment, a sole AlN single crystal seed with a length of 12 mm was obtained on the tungsten (W) substrate. The low axial temperature gradient between material source and substrate can decrease the nucleation rate and growth rate, and the high radial temperature gradient of the substrate can promote the expansion of crystal size. Additionally, the crystallinity of the crystals grown under different thermal field conditions are analyzed and compared. The Raman results manifest the superiority of the thermal inversion method in the growth of high quality AlN single crystal.